A man sneaked into the Forbidden Palace on the evening on the fourth day of the fifth month in the 43rd year of the reign of Emperor Shenzong of the Ming Dynasty (1368-1644). Armed with a stick and storming on his way to the Palace of Compassion and Tranquility where the crown prince lived， he was stopped by a guard. The man assaulted and injured the guard and stormed into the compound. He was captured under the front eave of the palace by another guard and several eunuchs. After being trussed with a rope， the assaulter was handed over to the commander of the guards at the Donghua Gate.

The next day the prince reported the assault case to the emperor， who immediately ordered to investigate the assault.

Liu Tingyuan， the security chief on that day in charge of security affairs of the Forbidden City， acted as the chief interrogator. The man said his name was Zhang Chai. Zhang Chai looked crazy and talked incoherently. Liu Tingyuan， however， observed that the man was not insane at all. The crafty assaulter was a mystery. Liu thought more investigation was needed and the man should be punished seriously. He reported his observation and tentative conclusions to the emperor.

On the 10th day of the fifth month， Hu Shixiang， Yue Junsheng and Lao Yongjia interrogated Zhang Chai together. Now Zhang’s confession was coherent. He said his fodders and firewood were burned by two men. He was so angry that he came to the capital city to sue the two arsonists. He wandered in the city for two days， without knowing how to proceed. He was then advised by two strangers that he should carry a stick made of a jujube tree branch， which could serve as a statement of charges. Zhang Chai said that was how the assault happened. Hu Shixiang and his two colleagues sentenced the man to death on the basis of Zhang’s confession and according to law.

Many officials were suspicious about the interrogation and verdict. They had a reason for suspicion. Although the dynasty had had the crown prince for a long while， the emperor treated the crown prince rather coldly. There was a suspicion that behind the assault was a conspiracy by Lady Zheng and her brother Zheng Guotai against the crown prince. It was widely known that Lady Zheng wished to have her son established as the crown prince. Ministers thought it suspicious to sentence Zhang Chai to death without further investigation to see if there was someone behind the assault. Wang Zhicai， a high-ranking official at the law department， wanted to investigate more.

Wang interrogated Zhang Chai and made a report to the emperor. Zhang changed his confession several times until Wang threatened to give him no meals until he would confess. Zhang said a eunuch brought him to the capital and another eunuch instructed him to storm the palace and kill anyone who wanted to stop him. The two eunuchs even promised to save his life if he killed anyone. Wang remarked that Zhang Chai was not insane at all and suggested that the emperor and ministers hear the case at a morning session or that the emperor instruct top judges to hear the case. The report and the suggestion were ignored by the Emperor.

On the 18th day of the fifth month some ministers appealed to the emperor， arguing that the case should be further investigated. The emperor was disgusted with some phrases in the appeals and decided to ignore their appeal. The magistrate of Jizhou where Zhang Chai came from checked on the confession and made a report， saying that Zhang was hated by villagers because he made a profit in a business of buying and selling firewood for a Buddhist temple construction project supervised by a eunuch， and that Zhang reported the burning to the eunuch in the hope of getting support from the eunuch who， however， chided him instead of giving him expected support， and that Zhang was so enraged that he came to Beijing to complain to the emperor. The judges who had sentenced Zhang to death now maintained their verdict on the basis of the magistrate’s report on the charge of insanity.

On the 21st day of the fifth month， 18 officials of the law department heard the case again. This time Zhang Chai named the names of the two eunuchs and another five men and described how they instructed him to kill the crown prince. The emperor instructed twice to look into the case thoroughly and find out the mastermind.

Zheng Guotai， the brother of Lady Zheng， became quite disturbed by the progress of the investigation. He wrote to the emperor to claim his innocence and defend himself against the suspicion. The letter to the emperor caused an uproar among the court. Zhang Chai and those allegedly involved in the assault had not named Zheng Guotai as the man behind the assault. Now Zheng’s self-defense seemingly incriminated himself. He Shijin， a minister， submitted a proposal to the emperor， saying that the case should be thoroughly investigated to clear Zheng Guotai if he was really innocent or punish him if he was proved to have been involved. He Shijin also suggested tightening security so that Zhang Chai would not die unexpectedly. This proposal was ignored by the emperor.

On the 28th day of the fifth month， the emperor and the crown prince and the crown prince’s two sons met with all the top-ranking officials at the palace. The emperor said that he loved the crown prince and that the crown prince treated him like a dutiful son. The crown prince said he was a dutiful son and he loved his father. The meeting with the ministers was designed to appease them so that they could see that the emperor did not want to depose the crown prince. The emperor and the crown prince remarked that Zhang Chai and his accomplice be executed and no one else should be involved.

On the 29th day， Zhang Chai was executed. The next day， high-ranking officials heard the case against the five men involved. As Zhang Chai was dead， the five men all said Zhang’s allegation was 1. Before the hearing could proceed further， the officials received an instruction from the crown prince. The crown prince argued the case in writing， saying that Zhang Chai might have deliberately revenged against the men who had treated him unfairly. The crown prince instructed the judges to confine the investigation to the five men and the five should be saved from severe punishment. Given the instruction of the crown prince， the ministers decided to stop further investigation and put an end to the hearing that day.

On the 13th day of the sixth month， the law department sentenced three of the five men to exile and the other two who had burned the firewood of Zhang Chai to whipping as punishment. The emperor approved the decision. The two eunuchs were executed secretly.

Before the case， the emperor had not seen his ministers for 15 years. As the two eunuchs were eunuchs working for Lady Zheng， the emperor came to see his ministers in order to protect Lady Zheng and her brother Zheng Guotai. Although the case was put to end， the conflict among court officials on the issue was still fierce， causing further infighting and resulting in serious political consequences for years. Some were demoted， or jailed， or exiled， some were later restored and rehabilitated， and some were promoted.□